WL has some specific features that are of particular interest and that are not possible to my knowledge in SL. Application sharing is one. Being able to share any application that runs in X11 has profound implications for distance learning. and social computing. Using VNC, a MS-Windows desktop and associated applications can also be shared. Collaborative whiteboards, videos, PDFs... So much is possible.
As a mini use case, imaging opening a shared browser in WL. This provides for novel and interesting distance learning configurations. A Blackboard or Sakai discussion board could be opened and used as a point of departure for virtual discussion. A PowerPoint slideshow could be presented at a distance and learners could have the opportunity to ask questions and receive feedback in real-time. Simulations could be incorporated for experiential learning. Three dimensional, collaborative concept mapping could also be incorporated. Again, so much is possible. This makes WL a truly exciting learning platform.